1. Field of the Invention
This invention relates generally to pipeline pressure testing methods and apparatus, and more particularly to an apparatus and method for pigging, flooding, and pressure testing pipelines utilizing a sliding sleeve valve at the end of a pig receiver which automatically opens upon fluid pressure in a pipeline reaching a predetermined limit allowing fluid trapped in the pipeline to escape, and is then automatically closed when a pig enters the pig receiver to allow pressure testing of the pipeline.
2. Brief Description of the Prior Art
All hazardous liquid, natural gas, and other gas pipelines are required by government regulations to be pressure tested after construction and prior to being placed into service. Most prior art methods of pressure testing require human intervention to manually open and close a valve at the downstream end of the pipeline during the testing operation. The testing operation is considerably expensive, particularly with subsea pipelines, due to the equipment, and manpower required.
Typically, the subsea pipeline is installed on the sea floor to extend from a production facility to a downstream facility, such as an existing pipeline system or a well manifold. Conventional prior art methods of pressure testing the pipeline require a test crew on a production facility at the upstream end of the pipeline and a separate support vessel and a separate crew of divers or a remote operated vehicle (ROV) to be positioned at the submerged downstream end of the pipeline to manually operate a valve at the submerged downstream end.
In the conventional pigging, flooding, and pressure testing operation, a pig launcher is connected to the upstream end of the pipeline and a pig receiver and conventional ball valve or gate valve is connected to the downstream end. During the testing operation the support vessel or ROV system is positioned above the submerged downstream end of the pipeline. A pipeline pig is forced through the pipeline by hydraulic pressure from fluid being pumped into the upstream end behind the pig. As the pig is being forced down the pipeline, the fluid (air and/or liquid) trapped in the pipeline between the pig and the receiver becomes pressurized. One or more divers, or a ROV is sent down to open the valve to allow the trapped air or fluid to escape while fluid continues to be pumped into the pipeline until the pig enters the receiver. The valve is then manually closed and the pressure in the pipeline is increased to the required test pressure. The pressure test is then performed and monitored by the test crew on the production facility.
The present apparatus and method eliminates the need and expense of a crew, and/or a separate support vessel with divers or an ROV at the downstream end of the pipeline. This is accomplished by utilizing a sliding sleeve valve which automatically opens upon fluid pressure in the pipeline reaching a predetermined limit allowing the fluid trapped in the pipeline to escape, and is then automatically closed when the pig enters the pig receiver to allow pigging, flooding, and pressure testing of the pipeline without human intervention at the downstream end.